In the pattern drawing apparatus of this type, by taking it into consideration that a positional relationship among components becomes different from designed values at an actual drawing stage, normally, corresponding positional shifts are preliminarily detected, so that the drawing positions are corrected.
For example, Japanese Patent Application Laid-Open Publication No. 2008-65034 (Patent Document 1) has disclosed a pattern drawing apparatus designed such that, by respectively detecting a positional shift between a camera for reading an alignment mark (hereinafter, referred to simply as “AM”) which is formed on a substrate and serves as a reference for adjusting a position and a calibration pattern for positional shift detection, and a positional shift between a pulse light beam of the optical head and the calibration pattern, a positional shift between the AM camera and the optical head relative to designed values can be detected.
The positional shift detecting operations are desirably carried out in a state close to an actual drawing operation; if not so, even a difference in detection timing would cause a positional shift. More specifically, a time lag between an operation of relatively moving the worktable with respect to the optical head and irradiation timing in the laser irradiation system causes a positional shift. In a case in which a pattern drawing process with higher accuracy is required, this positional shift cannot be ignored; however, the positional shift detection system according to Patent Document 1 completely fails to take this problem into consideration.